The present invention relates to analysis of an image that includes text.
Tanaka et al., U.S. Pat. No. 4,847,912, describe a technique of detecting a space between words with an optical character reader. As shown and described in relation to FIGS. 2-6, the reader scans each printed line in the direction of its height from its beginning to its end sequentially at a predetermined interval. The intervals are identified either as containing a printed part, represented by a black bit, or as being all white, represented by a white bit. The number of continuous white bits between black bits is counted. The histogram of the counts has two peaks corresponding to gaps between letters and gaps between words. The histogram is used to determine a threshold value for detecting a space between words, so that the beginning of each word can be identified.
Blum et al., U.S. Pat. No. 4,610,025, describe cryptographic analysis techniques. As shown and described in relation to FIGS. 3-7 and 9, a bit-mapped representation of an input page is broken into discrete glyph elements for further processing. As described in relation to FIG. 3, simple horizontal segmentation is performed, the shortest height glyph-line is selected, close line height analysis of selected lines is performed, whether any glyph line is a multiple of the height of the shortest glyph line is determined, overly high lines are selected, and vertical segmentation is performed. FIG. 4 illustrates simple horizontal segmentation, including recording the number of white or noise scan lines passed before encountering the first non-white/non-noise scan line or between glyph lines and also recording the number of lines separating. FIG. 4 also illustrates measuring the height of a glyph line in terms of the number of horizontal scan lines separating its uppermost and lowermost scan lines. FIG. 5 illustrates close line height analysis to determine whether a selected glyph line contains only a single line of text, based on horizontal distribution statistics from counts of black pixels occurring along scan lines. FIG. 6 illustrates vertical segmentation by analyzing the vertical white spacing located between glyphs in a line of text and by locating the larger white spaces to determine glyph words and blocks of glyph words. Vertical segmentation is performed by forming vertical scan lines and finding non-white/non-noise vertical scan lines to locate the leftmost and rightmost scan lines of each glyph and by counting the number of white or noise scan lines between glyphs. FIG. 7 illustrates operations that include determining the height and width of a glyph by counting pixels or scan lines and storing statistics descriptive of the glyph. As shown and described in relation to FIG. 2, the statistics about the glyphs can be used to obtain median width of glyphs on a page.
Tsuji, U.S. Pat. No. 4,594,732, describes letter pitch detection techniques. As shown and described in relation to FIGS. 1-2, the locations, heights, and widths of a series of letter blocks are detected and an effective one-letter width interval is determined on the basis of the frequency of occurrence (frequency distribution) of the widths of the series of letter blocks. The space widths are also used.